The present invention relates to implantable stroke treating devices, and more specifically is concerned with a device for reducing the risk of embolic material entering into the internal carotid artery of an individual and blood clots (collectively and interchangeably referred to as xe2x80x9cembolic materialxe2x80x9d).
A major portion of blood supply to the brain hemispheres is by two arteries, referred to as common carotid arteries (CCA), each of which branches off, or bifurcates as the term is at times used, into a so-called internal carotid artery (ICA) and an external carotid artery (ECA). Blood to the brain stem is supplied by two vertebral arteries.
Cerebralvascular diseases are considered among the leading causes of mortality and morbidity in the modern age. Strokes denote an abrupt impairment of brain function caused by pathologic changes occurring in blood vessels. The main cause of strokes is insufficient blood flow to the brain (referred to as xe2x80x9can ischemic strokexe2x80x9d) which are about 80% of stroke cases.
Ischemic strokes are caused by sudden occlusion of an artery supplying blood to the brain. Occlusion or partial occlusion (stenosis) are the result of diseases of the arterial wall. Arterial atherosclerosis is by far the most common arterial disorder, and when complicated by thrombosis or embolism it is the most frequent cause of cerebral ischemia and infarction, eventually causing the cerebral stroke.
Cardioembolism causes about 15%-20% of all strokes. Stroke caused by heart disease is primarily due to embolism of thrombotic material forming on the atrial or ventricular wall or the left heart valves. These thrombi then detach and embolize into the arterial circulation. Emboli large enough can occlude large arteries in the brain territory and cause strokes.
Cardiogenetic cerebral embolism is presumed to have occurred when cardiac arrhythmia or structural abnormalities are found or known to be present. The most common causes of cardioembolic stroke are nonrheumatic (non-valvular) atrial fibrillation (AF), prothestic valves, rheumatic heart disease (RHD), ischemic cardiomyopathy, congestive heart failure, myocardial infarction, port-operatory state and protruding aortic arch atheroma (A.A.A.).
Such disorders are currently treated in different ways such as by drug management, surgery (carotid endarterectormy) in case of occlusive disease, or carotid angioplasty and carotid stents.
While endarterectomy, angioplasty and carotid stenting are procedures targeting at opening the occluded artery, they do not prevent progression of new plaque. Even more so, the above treatment methods only provide a solution to localized problems and do not prevent proximal embolic sources, i.e., embolus formed at remote sites (heart and ascending aorta) to pass through the reopened stenosis in the carotid and occlude smaller arteries in the brain. This is a substantial problem, inasmuch as about one-third of patients suffering from carotid occlusion also have proximal embolic sources leading to stroke. It should be noted that only about 20% of the cases of stroke result from an occlusion of the carotid.
It will also be appreciated that endarterectomy is not suitable for intracarnial arteries or in the vertebrobasilar system since these arteries are positioned within unacceptable environment (brain tissue, bone tissue) or are too small in diameter.
Introducing filtering means into blood vessels, in particular into veins, has been known for some time. However, filtering devices known in the art are generally of a complex design, which renders such devices unsuitable for implantation within carotid arteries, and unsuitable for handling fine embolic material. However, when considering the possible cerebral effects of even fine embolic material occluding an artery supplying blood to the brain, the consequences may be fatal or may cause irreversible brain damage.
However, in light of the short period of time during which brain tissue can survive without blood supply, there is significant importance to providing suitable means for preventing even small embolic material from entering the internal carotid artery, so as to avoid brain damage.
A drawback of prior art filtering means is their tendency to become clogged. On the one hand, in order to provide efficient filtering means, the filter should be of fine mesh. On the other hand, a fine mesh has a higher tendency toward, and risk of, occlusion.
It should also be noted that the flow ratio between the ICA and the ECA is about 4:1. This ratio also reflects the much higher risk of embolic material flowing into the ICA.
It is thus an object of the present invention to provide an implantable deflecting device suitable to be positioned within a blood vessel supplying blood to the brain, and further suitable to deflect embolic material that would have flown into the internal carotid artery, into the external carotid artery, thereby preventing the entry of said embolic material into the internal carotid artery, and thus preventing extracarnial embolus to occlude small intercarnial arteries in the brain.
It is another object of the invention to provide a method for treating a patient known to suffer from embolic diseases, by selectively occluding the passage of embolic material into the internal carotid artery.
It is yet another object of the invention to provide a method for preventing conditions associated with embolic material.
Other objects of the invention will become apparent as the description proceeds.
The present invention provides an implantable device for positioning in the vicinity of the bifurcation of the common carotid artery (CCA) into the internal carotid artery (ICA) and the external carotid artery (ECA), comprising a deflecting element suitable to deflect the flow of embolic material flowing in the CCA toward the ICA, into the ECA. Preferably, but non-limitatively, the deflecting element comprises filtering means.
Thus, in one aspect, the invention provides an implantable deflecting device comprising an anchoring member engageable with inner walls of a carotid artery, and one or more deflecting members for deflecting flow of embolic material into the ECA, substantially without obstructing blood flow into the ICA.
According to the invention there is thus provided an implantable device for positioning about a blood vessel bifurcation zone to control flow of embolic material around said bifurcation, the device comprising:
an anchoring element extending within said zone of bifurcation to anchor said device therein, and a deflecting element, associated with said anchoring element, said deflecting element comprising a mesh having a mesh size sufficient to allow passage of blood without hindrance whilst occluding passage of embolic material exceeding a predetermined size.
The anchoring member and the deflecting member may be integral with one another or attached or coupled to one another. In the present specification the anchoring member and the deflecting member may be referred to also as anchoring portion and deflecting portion, respectively.
In accordance with a particular preferred embodiment of the invention, the deflecting member is a screening element fitted at the inlet into the ICA and is adapted to prevent the passage into the ICA of embolic material above a predetermined size.
By a preferred embodiment, at least the anchoring member is a stent adapted for insertion via the vasculature of an individual. The implantable deflecting device in accordance with any of the embodiments of the present invention may be permanently implanted or may be removed after a period of time, depending on the course of treatment and the medical procedure.
As will become evident from the description to follow, the deflecting member is preferably, but not compulsorily, positioned at the inlet into the internal carotid artery, whereas the anchoring member may be positioned in a variety of locations. The deflecting member, however, may be positioned at any location that fulfills two conditions: firstly, it does not occlude the flow of blood into the ICA, and secondly, it causes a deflection of the flow of embolic material into the ECA. For instance, the deflecting member may be anchored in the ICA and protrude into the bifurcation zone, or may be positioned at the entrance to the ECA and extend toward the surrounding walls, for constructive and strength reasons.
In accordance with one specific embodiment of the invention, the anchoring member comprises a tubular portion for anchorage within the CCA with an upstream portion extending towards the bifurcation zone, said upstream portion accommodating the one or more deflecting member.
In accordance with still another preferred embodiment of the invention, the anchoring member comprises at tubular portion for anchoring within the ECA, with a downstream portion extending towards the bifurcation zone, said downstream portion accommodating the one or more deflecting member. Alternatively, the anchoring member comprises a tubular portion for anchorage within the ICA, with a downstream portion extending towards the bifurcation zone, said upstream portion accommodating the one or more deflecting member.
It will also be appreciated that the anchoring member may comprise a tubular portion for anchorage within a vascular portion extending along the CCA and the ECA, wherein the one or more deflecting members is accommodated at the inlet to the ICA.
By one specific design the anchoring member comprises a tubular portion for anchorage at the bifurcation zone, wherein the one or more deflecting member is accommodated at or adjacent the inlet into the ICA.
The one or more deflecting member may be integrally formed with the anchoring member or may be attached or coupled thereto either during manufacture, or after implanting the anchoring member within the artery.
By another aspect of the present invention there is provided an implantable deflecting device for implanting at the vicinity of bifurcation of the common carotid artery (CCA) into the internal carotid artery (ICA) and the external carotid artery (ECA); the device comprising an anchoring member engageable with inner walls of a carotid artery, and one or more deflecting members, wherein the one or more deflecting member is so positioned and sized so that embolic material encountering it is deflected to flow into the ECA.
In another aspect the invention is directed to an arterial stent suitable to be positioned in the vicinity of the bifurcation of the common carotid artery (CCA) into the internal carotid artery (ICA) and the external carotid artery (ECA), comprising a deflecting device.
The invention is further directed to an arterial stent suitable to be positioned in the vicinity of the bifurcation of the common carotid artery (CCA) into the internal carotid artery (ICA) and the external carotid artery (ECA), coupled to a deflecting device.
Preferably, but non-limitatively, the aforementioned stents employ as a deflecting device an element comprising filtering means of dimensions suitable to allow the flow of blood to proceed into the ICA, while preventing the access thereto of embolic material of a predetermined size.
In a further aspect, the invention is directed to the prevention of the occurrence, or the recurrence, of cerebralvascular diseases, particularly of stroke, comprising preventing the flow of embolic material flowing in the CCA from accessing the ICA, by deflecting the flow of said embolic material into the ECA. Prevention of the cerebralvascular disease is achieved by implanting, permanently or temporarily, in the vicinity of the bifurcation of the common carotid artery (CCA) into the internal carotid artery (ICA) and the external carotid artery (ECA), a deflecting device according to the invention.
It should be emphasized that while throughout this specification reference is made to the bifurcation of the CCA into the ICA, this is done for the sake of brevity only, but the invention is in no way limited to this specific location. The invention can advantageously be exploited at any other suitable bifurcation of blood vessels as existing, for instance, in the leg.
All the above and other characteristics and advantages of the invention will be better understood through the following illustrative and non-limitative detailed description of preferred embodiments thereof.